This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-181630, filed Jun. 15, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a press-forming machine for manufacturing a formed product made of glass such as an optical lens and prism, and more particularly, to a mechanism for taking out a product from a die after press forming.
2. Description of the Related Art
Not only a polishing method but also a re-heat press forming method is employed to manufacture an optical element made of glass such as an optical lens or prism, which must be formed with high accuracy of dimension. In the re-heat press forming method, glass as a raw-material is melted and solidified in a mold to obtain a preform roughly shaped. The preform was further heated and press-formed by use of dies, thereby transferring the patterns of the dies to the glass. In this manner, the optical element is formed.
Since the re-heat press forming method requires only one press-forming step for forming a curved surface, the productivity is high. Also, this method requires no polishing step. Therefore, an optical element can be manufactured under clean environment. Furthermore, once dies are manufactured, a large number of formed products can be efficiently manufactured in accordance with accuracy varied depending upon dies.
For example, when an optical lens is manufactured by press forming, more specifically, when the upper and lower optical surfaces and side surface of the optical lens are simultaneously formed, a formed product is usually taken out from the lower die by using a vacuum chuck, after the pressing and cooling steps are completed and the dies are opened. However, there is a problem in this case. Since the formed product is buried in the cavity of the lower die, it is not easy to be taken out. As a result, a device for supplying a preform and taking out a formed product must be formed with a more complicated structure, and much time is required for collecting the formed products.
A formed product may be taken out by pushing it by an ejector pin in the same manner as in an injection-molding machine. However, this method has a problem in that a formed product may be scratched or fractured by the ejector pin, which comes directly in touch with the optical surface of the formed product.
The inventions described and/or claimed herein have been achieved in view of the problems of conventional press forming of glass, as mentioned above. An object of the present invention is to provide a press-forming machine for glass provided with a structural element facilitating taking-out of a press-formed product from a die.
A press forming machine for glass according to the present invention is used for performing press-forming of glass at elevated temperature by using an upper die supported by an upper shaft from an upper surface side and a lower die supported by a lower shaft from a lower surface side.
The lower die comprises:
a core having a pattern on an upper surface;
a cavity die surrounding the outer periphery of the core and guiding the core along the outer periphery; and
a die plate supporting the core and the cavity die from the lower-surface side and having a vertically extended through-hole formed therein.
In the press-molding machine, a vertically movable ejector pin is installed within the lower shaft, the tip of the ejector pin being inserted into the through-hole, and a formed product is pushed out from the cavity die by pushing up the core by the ejector pin.
According to the press-forming machine for glass of the present invention, after pressing and cooling steps are completed and the dies are opened, the ejector pin is moved to push up the core, thereby pushing out a formed product from the cavity die. In this manner, formed products can be easily taken out from the press-forming machine and collected, by using, for example, an automatic transfer apparatus.
In the aforementioned configuration, the lower die may be substituted by an upper die formed of the same structural elements as those of the lower die, namely, a core, cavity die and die plate. Further, the upper shaft is equipped with an ejector pin for pushing down the core installed therein.
A plurality of formed products can be simultaneously manufactured by fitting a plurality of cores to the upper and lower dies.
In this case, the lower die preferably comprises:
a plurality of cores each having a pattern on an upper surface thereof;
a cavity die having a plurality of first opening portions at an upper surface side and a second opening portion at the lower surface side, each of the first opening portions communicating with the second opening portion and guiding the corresponding core from an outer peripheral side;
a slide plate housed in the second opening portion and supporting each of the plurality of cores from a lower surface side; and
a die plate supporting the slide plate and cavity die from the lower surface side and having a vertically extended through-hole formed therein.
In this case, a vertically movable ejector pin is installed within the lower shaft, the tip of the ejector pin being inserted into the through-hole, and a formed product is pushed out from the cavity die by pushing up the core via the slide plate by the ejector pin.
In the aforementioned configuration, the lower die may be substituted by an upper die formed of the same structural elements as those of the lower die, namely, cores, a cavity die, die plate and slide plate. Further, the upper shaft is equipped with an ejector pin for pushing down the cores therein.